1. Technical Field
The present invention relates to a silicon nitride-melilite composite sintered body effectively applicable as a structural material of a semiconductor inspection device, such as a probe card, as well as to a device, such as a probe card, utilizing such a silicon nitride-melilite composite sintered body.
2. Description of the Related Art
In the process of manufacturing semiconductor chips, a semiconductor inspection device, for example, a probe card, is generally used to check for the normal operations of an integrated circuit formed on each silicon wafer or semiconductor wafer. The probe card typically has a large number of needle-like probe terminals provided on a lower face of a ceramic substrate made of, for example, alumina. The probe terminals are brought into contact with terminal pads of the semiconductor wafer. The semiconductor wafer is checked for conduction of the integrated circuit and insulation between respective circuits by application of electric current.
The inspection of the operating conditions of the integrated circuit formed on the semiconductor wafer may be required not only at ordinary temperature but in a high temperature condition of not lower than 100° C. (for example, 150° C.). In the latter case, the probe card is required to quickly increase its temperature with a temperature increase of the semiconductor wafer and have a practically equivalent behavior of thermal expansion to that of the semiconductor wafer. The different behaviors of thermal expansion may cause poor contact of the probe terminals of the probe card with the terminal pads of the semiconductor wafer. There is accordingly a high demand for a probe card having a practically equivalent thermal expansion coefficient to that of the semiconductor wafer and a ceramic material used to manufacture such a probe card. The desired ceramic material accordingly has a sufficiently high mechanical strength and an average thermal expansion coefficient that is arbitrarily adjustable in a range of 2 to 6 ppm/K or more preferably in a range of 3 to 5 ppm/K according to the demand characteristics of the device in a temperature range from room temperature (e.g., 23° C.) to 150° C.
One proposed probe card utilizes a ceramic substrate made of a non-oxide ceramic material, such as aluminum nitride or silicon nitride, to allow for inspection of integrated circuits in the high temperature condition. This prior art probe card has excellent thermal conductivity but only a substantially fixed thermal expansion coefficient. For example, in the case of application of aluminum nitride as the ceramic material, the thermal expansion coefficient of the probe card is approximately 4 ppm/K, which is relatively close to the thermal expansion coefficient of the semiconductor wafer but is not adjustable to another arbitrary value. Namely this prior art technique does not fulfill the recent high demand for the probe card. In the case of application of silicon nitride as the ceramic material the thermal expansion coefficient of the probe card is undesirably low as 2 ppm/K or below. Alumina widely used as an oxide ceramic material of the ceramic substrate, on the other hand, has an undesirably high thermal expansion coefficient of about 6 ppm/K or above.
The ceramic material having the sufficiently high mechanical strength and the average thermal expansion coefficient that is arbitrarily adjustable in the range of 2 to 6 ppm/K in the temperature range from room temperature to 150° C. is highly demanded for the probe card or another equivalent device used for inspection of semiconductor wafers.
One proposed example of the silicon nitride-based ceramic material has a thermal expansion coefficient in a range of 3.5 to 4.1 ppm/K, which practically satisfies the above condition of the average thermal expansion coefficient in the range of 2 to 6 ppm/K. This prior art silicon nitride-based ceramic material, however, does not have a sufficiently high Young's modulus, which is lately required for large-scaled ceramic substrates.
As a result of the intensive studies and researches for development of a ceramic material satisfying the diverse conditions mentioned above, the inventors of the present invention have found that composing silicon nitride and a melilite at a specific composition gives a composite sintered body having a high mechanical strength, a high Young's modulus, and excellent sintering performance or production stability, as well as an average thermal expansion coefficient arbitrarily adjustable to the above range of 2 to 6 ppm/K in the temperature range from room temperature to 150° C.